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<title>Conditionals (Using the GNU Compiler Collection (GCC))</title>

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<h3 class="section" id="Conditionals-with-Omitted-Operands"><span>6.8 Conditionals with Omitted Operands<a class="copiable-link" href="#Conditionals-with-Omitted-Operands"> &para;</a></span></h3>
<a class="index-entry-id" id="index-conditional-expressions_002c-extensions"></a>
<a class="index-entry-id" id="index-omitted-middle_002doperands"></a>
<a class="index-entry-id" id="index-middle_002doperands_002c-omitted"></a>
<a class="index-entry-id" id="index-extensions_002c-_003f_003a"></a>
<a class="index-entry-id" id="index-_003f_003a-extensions"></a>

<p>The middle operand in a conditional expression may be omitted.  Then
if the first operand is nonzero, its value is the value of the conditional
expression.
</p>
<p>Therefore, the expression
</p>
<div class="example smallexample">
<pre class="example-preformatted">x ? : y
</pre></div>

<p>has the value of <code class="code">x</code> if that is nonzero; otherwise, the value of
<code class="code">y</code>.
</p>
<p>This example is perfectly equivalent to
</p>
<div class="example smallexample">
<pre class="example-preformatted">x ? x : y
</pre></div>

<a class="index-entry-id" id="index-side-effect-in-_003f_003a"></a>
<a class="index-entry-id" id="index-_003f_003a-side-effect"></a>
<p>In this simple case, the ability to omit the middle operand is not
especially useful.  When it becomes useful is when the first operand does,
or may (if it is a macro argument), contain a side effect.  Then repeating
the operand in the middle would perform the side effect twice.  Omitting
the middle operand uses the value already computed without the undesirable
effects of recomputing it.
</p>
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